US20090034406A1 - Optical information reproducing system - Google Patents

Optical information reproducing system Download PDF

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Publication number
US20090034406A1
US20090034406A1 US12/181,223 US18122308A US2009034406A1 US 20090034406 A1 US20090034406 A1 US 20090034406A1 US 18122308 A US18122308 A US 18122308A US 2009034406 A1 US2009034406 A1 US 2009034406A1
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US
United States
Prior art keywords
optical
groove
recording medium
information recording
optical pickup
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Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US12/181,223
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English (en)
Inventor
Atsuo Shimizu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Taiyo Yuden Co Ltd
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Taiyo Yuden Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
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Publication date
Application filed by Taiyo Yuden Co Ltd filed Critical Taiyo Yuden Co Ltd
Publication of US20090034406A1 publication Critical patent/US20090034406A1/en
Assigned to TAIYO YUDEN CO., LTD. reassignment TAIYO YUDEN CO., LTD. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: SHIMIZU, ATSUO
Abandoned legal-status Critical Current

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B7/00—Recording or reproducing by optical means, e.g. recording using a thermal beam of optical radiation by modifying optical properties or the physical structure, reproducing using an optical beam at lower power by sensing optical properties; Record carriers therefor
    • G11B7/08—Disposition or mounting of heads or light sources relatively to record carriers
    • G11B7/09—Disposition or mounting of heads or light sources relatively to record carriers with provision for moving the light beam or focus plane for the purpose of maintaining alignment of the light beam relative to the record carrier during transducing operation, e.g. to compensate for surface irregularities of the latter or for track following
    • G11B7/0925—Electromechanical actuators for lens positioning
    • G11B7/0935—Details of the moving parts

Definitions

  • the present invention relates to an optical-information reproducing system, which includes an optical-information recording medium and an optical disk apparatus, for reproducing information that is recorded on the optical-information recording medium.
  • a write-once compact disk (a so-called compact-disk recordable (CD-R) disk) has the following configuration: a spiral groove, to which an optical head is guided and which is used to record information, is provided in one surface of an optically transparent substrate having a diameter of 12 cm and a thickness of 1.2 mm; and a recording layer and a reflecting layer are formed in this order on a surface in which the groove is formed.
  • the groove has a wobble which is formed in such a manner that meandering is repeated at a fixed period along a running direction in order to allow accurate position information to be obtained.
  • the groove is also referred to as a “track”.
  • the groove has a trapezoid shape in the running direction.
  • the top is broadly opened, and the bottom surface is slightly narrower.
  • Laser light having a wavelength of typically about 780 nm is irradiated from the other surface side of the optically transparent substrate, whereby data is recorded in and/or reproduced from the recording layer.
  • a write-once digital-versatile disk (a so-called digital-versatile disk recordable (DVD-R) disk) has the following configuration: a spiral groove having a wobble is provided in one surface of an optically transparent substrate having a diameter of 12 cm and a thickness of 0.6 mm as in the above-mentioned case, and the pitch of the groove is lower than half that of the groove of the CD-R; a recording layer and a reflecting layer are formed in this order in a surface in which the groove is formed; and a dummy substrate having a diameter 12 cm and a thickness of 0.6 mm is attached to the top of the reflecting layer.
  • Laser light having a wavelength of typically about 630 nm to 680 nm is irradiated from the other surface side of the optically transparent substrate, whereby data is recorded in and/or reproduced from the recording layer.
  • a higher-order resonance having a frequency of about 10 kHz to 40 kHz have become a significant problem, which is mainly caused by elastic deformation of movable units (objective-lens-holding units) of optical-pickup-drive devices.
  • the higher-order resonance is a second- or higher-order resonance.
  • the higher-order resonance occurs at a frequency higher than that at which a first-order resonance occurs, and occurs due to elastic deformation in a mode different from the mode of elastic deformation in which the first-order resonance occurs.
  • a gain more particularly, a gain in a lower range
  • the difference (a gain margin) between a gain at a certain reference frequency (around a crossover frequency of a servo) and a gain at a peak of the higher-order resonance becomes small or negative. This leads to a problem that the tracking capability of the optical pickup is decreased, and that the optical pickup fails to track a groove.
  • a rotational speed is about 9.6 rps in an outer peripheral area (positioned at a radial distance of about 58 mm).
  • the rotational speed becomes about 24.2 rps in an inner peripheral area (positioned at a radial distance of about 23 mm).
  • a rotational speed in a case in which data is being recorded/reproduced in an inner peripheral area differs from a rotational speed in a case in which data is being recorded/reproduced in an outer peripheral area.
  • the rotational speed in a case in which data is being recorded/reproduced in an inner peripheral area is faster than that in a case in which data is being recorded/reproduced in an outer peripheral area.
  • the wobble frequency is typically about 140 kHz.
  • the wobble frequency decreases to about 56 kHz in accordance with a ratio of a rotational speed of about 9.6 rps in an area positioned at a radial distance of about 58 mm to a rotational speed of about 24.2 rps in an area positioned at a radial distance of about 23 mm.
  • the wobble frequency becomes lower than the higher-order resonance frequency of the optical pickup in some cases. In other words, the relationship that the wobble frequency ⁇ the higher-order resonance frequency is obtained.
  • the wobble frequency becomes equal to the higher-order resonance frequency.
  • a wobble signal WF is superimposed on the higher-order resonance frequency HF.
  • the peak of the higher-order resonance becomes higher, and the gain margin becomes small or negative. Accordingly, the tracking capability of the optical pickup is decreased, and the optical pickup fails to track the groove in some cases.
  • the optical-information recording medium that is rotated at a fixed linear velocity, there is a portion in which wobble groove portions of the groove that are adjacent to one another are close and have phases opposite to one another. In this portion, the optical pickup fails to track the groove more often.
  • an optical-information reproducing system in which information recorded on an optical-information recording medium can be reproduced by rotating the optical-information recording medium at a fixed velocity that is a linear velocity of 3.49 m/s and by causing an optical pickup to track a groove in order to irradiate the groove with laser light.
  • the optical-information recording medium includes the followings: an optically transparent substrate having a disk shape, one surface of which has a groove formed in a spiral shape, the groove having a wobble; a light-absorbing layer that is formed on the surface of the optically transparent substrate; and a light-reflecting layer that is formed on the light-absorbing layer.
  • a higher-order resonance frequency of the optical pickup that is generated in a case in which the optical pickup is caused to track the groove is made lower than a wobble frequency that is reproduced using the groove without performing rotation control on the optical-information recording medium.
  • the optical-information reproducing system according to the aspect of the present invention is particularly effective in a case in which the wobble frequency is a frequency that is reproduced using the groove when the optical pickup is caused to move from an outer peripheral area to an inner peripheral area of the optical-information recording medium and then is caused to track the groove in the inner peripheral area. Additionally, the optical-information reproducing system according to the aspect of the present invention is also effective in a case in which the higher-order resonance frequency of the optical pickup ranges from 40 kHz to 100 kHz.
  • the higher-order resonance frequency of the optical pickup is made lower than the wobble frequency, whereby a gain margin can be prevented from being decreased because of a peak of the wobble frequency. Because a decrease in the gain margin can be minimized, the tracking capability of the optical pickup is increased, and the number of occurrences in which the optical pickup fails to track the groove is reduced.
  • the optical-information reproducing system can be obtained, in which the tracking capability of the optical pickup can be increased, and in which the number of occurrences in which the optical pickup fails to track the groove can be reduced, by increasing the gain margin.
  • FIG. 1 is a functional block diagram of an optical-information reproducing system according to an embodiment of the present invention.
  • FIG. 2 is a schematic sectional view of an optical-information recording medium.
  • FIG. 3 illustrates a state in which an optical pickup is caused to track a groove.
  • FIG. 4 illustrates a state in which the optical pickup is caused to track a groove.
  • FIG. 5 is a graph that shows gain, and that shows a gain margin which is a difference between a gain around a crossover frequency of a servo and a gain at a higher-order resonance frequency.
  • FIG. 6 is a graph that shows gain, and that shows a gain margin in a case in which a wobble frequency is superimposed on the higher-order resonance frequency.
  • FIG. 1 is described below as a functional block diagram of a recording apparatus according to an embodiment of the present invention.
  • An optical-disk reproduction apparatus 100 includes a memory 126 , a processing section 125 , a laser-diode drive control section 122 , a data-demodulator circuit 123 , a characteristic-value detection section 124 , an optical pickup 110 , an optical-pickup drive control section 121 , a rotation control section (not shown) and a motor (not shown) that are used for an optical-information recording medium 150 , a servo control section (not shown) used for the optical pickup 110 , and so forth.
  • the processing section 125 includes a central processing unit (CPU) that performs processing, and a memory circuit in which a program that allows data processing to be performed is recorded.
  • the laser-diode drive control section 122 controls laser light for recording data and laser light for reproducing data.
  • the data-demodulator circuit 123 performs a predetermined decoding process on a reproduction signal that is output.
  • the characteristic-value detection section 124 detects the reproduction signal, thereby detecting a signal associated with focusing, tracking, or a wobble.
  • the optical-pickup drive control section 121 controls a direction of laser light irradiated from the optical pickup 110 .
  • the optical pickup 110 includes an objective lens 113 , a beam splitter 115 , a detection lens 114 , a collimator lens 112 , a laser diode 111 , a photodetector 116 , and an actuator 117 .
  • the actuator 117 is operated by control of the optical-pickup drive control section 121 , whereby focusing and tracking are performed.
  • the processing section 125 is connected to the memory 126 , the data-demodulator circuit 123 , the characteristic-value detection section 124 , the optical-pickup drive control section 121 , the laser-diode drive control section 122 , the rotation control section and the servo control section that are not shown, and so forth.
  • the characteristic-value detection section 124 is connected to the photodetector 116 and the processing section 125 .
  • the data-demodulator circuit 123 is connected to the photodetector 116 and the processing section 125 .
  • the optical-pickup drive control section 121 is connected to the processing section 125 and the optical pickup 110 .
  • the laser-diode drive control section 122 is connected to the processing section 125 and the laser diode 111 .
  • the processing section 125 is also connected to an input/output system (not shown) via an interface section (not shown).
  • the laser-diode drive control section 122 drives the laser diode 111 in response to an instruction issued by the processing section 125 to output the laser light for reproducing data.
  • the laser light for reproducing data is irradiated onto the optical-information recording medium 150 via the collimator lens 112 , the beam splitter 115 , and the objective lens 113 .
  • Light reflected on the optical-information recording medium 150 is input to the photodetector 116 via the objective lens 113 , the beam splitter 115 , and the detection lens 114 .
  • the photodetector 116 converts the light reflected on the optical-information recording medium 150 into an electric signal, and outputs the electric signal to the data-demodulator circuit 123 as a reproduction signal.
  • the data-demodulator circuit 123 performs the predetermined decoding process on the reproduction signal to obtain decoded data.
  • the decoded data is output to a display section of the input/output system (not shown) via the processing section 125 and the interface section (not shown), thereby displaying the reproduced data.
  • the optical-information recording medium 150 shown in FIG. 2 includes an optically transparent substrate 151 , which has a diameter of 12 cm, a thickness of 0.6 mm, and a disk shape, a light-absorbing layer 153 , and a light-reflecting layer 154 .
  • a spiral groove 152 having a wobble is formed in one surface of the optically transparent substrate 151 .
  • the light-absorbing layer 153 is formed on the surface of the optically transparent substrate 151 in which the groove 152 is formed.
  • the light-reflecting layer 154 is formed on the light-absorbing layer 153 .
  • a dummy substrate 156 which has a diameter of 12 cm, a thickness of 0.6 mm, and a disk shape, is attached to the top of the light-reflecting layer 154 via an adhesive layer 155 .
  • the optical-information recording medium 150 is rotated in such a manner that it has a linear velocity of 3.49 m/s when data is reproduced. Accordingly, regarding the relationship between the meander period of the groove 152 and line length corresponding to a circuit of the groove 152 , there are the following two states: a same-phase state, i.e., a state in which the meander periods of groove portions of the groove 152 that are adjacent to one another are substantially the same, as shown in FIG. 3 ; and an opposite-phase state, i.e., a state in which the meander periods of groove portions of the groove 152 that are adjacent to one another are shifted by a half period from one another, as shown in FIG. 4 .
  • a same-phase state i.e., a state in which the meander periods of groove portions of the groove 152 that are adjacent to one another are substantially the same, as shown in FIG. 3
  • an opposite-phase state i.e., a state in which the meander periods of groove portions of the
  • the actual spacing of the groove portions of the groove 152 is narrower only by a meander amplitude of 2a ⁇ 2.
  • the narrower portion is a portion in which disturbance of a tracking signal easily occurs.
  • any one of various types of materials that are used as substrate materials of optical-information recording media in the related art can be selected as a substrate material of the optically transparent substrate 151 .
  • the substrate material include acrylic resins such as polycarbonate and polymethyl methacrylate. If necessary, substrates individually formed of the above-mentioned substrate materials may be stacked, resulting in a combination use of the substrate materials. From among the substrate materials, a thermoplastic resin is preferable in view of formability, moisture resistance, dimensional stability, low cost, and so forth. Polycarbonate is the most preferable material.
  • the optically transparent substrate 151 may be formed in the shape of a disk by injection molding or the like. It is preferable that the groove 152 , which is formed in one surface of the optically transparent substrate 151 , have, for example, a depth of 135 nm to 170 nm, and an amplitude of typically 20 nm to 35 nm (peak to peak).
  • the light-absorbing layer 153 be a recording layer having a coloring material, in which data can be recorded using pits that are formed by irradiating the light-absorbing layer 153 with laser light.
  • a coloring material in which data can be recorded using pits that are formed by irradiating the light-absorbing layer 153 with laser light.
  • an organic dye a phthalocyanine dye, a cyanine dye, an azo dye, or the like is preferable.
  • data information such as information concerning a music piece, an image, or a computer program can be recorded in the light-absorbing layer 153 and/or reproduced from the light-absorbing layer 153 .
  • the light-absorbing layer 153 may be formed as follows: an application liquid is prepared by dissolving the coloring material together with a binder or the like in an appropriate solvent; next, the application liquid is applied, by spin coating, screen printing, or the like, over the surface of the optically transparent substrate 151 in which the groove 152 is formed, resulting in formation of a coating film; and after that, the coating film is dried out.
  • the light-reflecting layer 154 reflects the laser light for recording data and/or the laser light for reproducing data.
  • a metallic film formed of, for example, Au, Al, Ag, Cu, or Pb, an alloy film formed of Au, Al, Ag, Cu, or Pb, an alloy film formed by adding a minor component to Au, Al, Ag, Cu, or Pb, or the like is preferable.
  • the light-reflecting layer 154 be formed, for example, by ion plating, sputtering, or the like, on the surface of the optically transparent substrate 151 in which the groove 152 is formed. More particularly, sputtering is the most preferable technique in view of mass productivity, and cost.
  • the dummy substrate 156 is used to match the entire thickness of the optical-information recording medium 150 to the thickness of a CD-R.
  • the diameter and thickness of the dummy substrate 156 are the same as those of the optically transparent substrate 151 .
  • a substrate material of the dummy substrate 156 a substrate material similar to that of the optically transparent substrate 151 can be used. More specifically, examples of the substrate material include acrylic resins such as polycarbonate and polymethyl methacrylate. If necessary, a plurality of substrates individually formed of the above-mentioned substrate materials may be used, resulting in a combination use of the substrate materials.
  • thermoplastic resin is preferable in view of formability, moisture resistance, dimensional stability, low cost, and so forth.
  • Polycarbonate is the most preferable material.
  • the dummy substrate 156 is attached to the top of the light-reflecting layer 154 via the adhesive layer 155 that is formed of an optically transparent hardening resin.
  • a photo detector unit PD is divided into four areas as shown in FIGS. 3 and 4 . In each of the areas, a corresponding one of intensities of the reflected light can be detected.
  • the reflected light which is reflected from the optical-information recording medium 150 , is detected by the photodetector 116 , and is converted into an electric signal.
  • the electric signal is input to the characteristic-value detection section 124 .
  • the characteristic-value detection section 124 generates a push-pull signal using the intensities of the reflected light, which are detected in the corresponding areas of the photo detector unit PD of the photodetector 116 , and inputs the push-pull signal to the processing section 125 .
  • the processing section 125 inputs a control signal to the optical-pickup drive control section 121 on the basis of the obtained push-pull signal.
  • the processing section 125 operates the servo control section (not shown) and the actuator 117 so that a beam spot BS can track the groove 152 .
  • the groove 152 is designed so as to have a meander period such that a wobble frequency becomes higher than 140 kHz when the optical-information recording medium 150 is rotated at a linear velocity of about 3.49 m/s.
  • the wobble frequency that is reproduced at an instant at which the optical pickup 110 is caused to track the groove 152 decreases to a value higher than that obtained in the related art.
  • the meander period of the groove 152 is about 280 kHz
  • a wobble frequency at an instant at which the optical pickup 110 is moved from the outermost periphery to the innermost periphery of a recording area of the optical-information recording medium 150 becomes about 110 kHz.
  • the lowest wobble frequency that is reproduced at an instant at which the optical pickup 110 of the optical-information recording medium 150 is caused to track the groove 152 can be made higher than a higher-order resonance frequency of the optical pickup 110 .
  • the gain margin is not influenced by the wobble frequency. Accordingly, the gain margin can be prevented from being decreased because of a peak of the wobble frequency, and a decrease in the gain margin can be minimized.
  • the higher-order resonance frequency of the optical pickup 110 can be made higher than about 40 kHz by reducing the weight of the objective lens 113 or by increasing the stiffness of an objective-lens-holding unit.
  • a method can be used, in which the weight of the objective-lens-holding unit of the objective lens 113 is reduced by forming the objective-lens-holding unit containing an aluminum material, or a resin material, compared with the weight of the objective-lens-holding unit formed of a metallurgical material such as iron.
  • a hard spring can be used.
  • the above methods can be used as methods for increasing the higher-order resonance frequency of the optical pickup 110 by suppressing vibration of the optical pickup 110 that occurs when the optical pickup 110 is moved between the outer and inter peripheries.
  • the methods for increasing the higher-order resonance frequency of the optical pickup 110 are not limited the above-mentioned methods, and various methods can be employed.
  • data of a DVD-R is reproduced at 8 ⁇ speed (inter periphery) or at 20 ⁇ speed (outer periphery), or when data of a blu-ray disk (BD) is recorded/reproduced
  • the higher-order resonance frequency of the optical pickup 110 ranges from about 40 kHz to about 100 kHz, the optical-information reproducing system according to the embodiment of the present invention is particularly effective.
  • the wobble frequency is described, which is reproduced using the groove when the optical pickup is moved from the outermost periphery to the innermost periphery of the recording area of the optical-information recording medium.
  • the present invention is not limited to the above-described embodiment.
  • the optical-information reproducing system according to the embodiment of the present invention is also effective in a case in which the optical pickup is moved from a recording area of the optical-information recording medium that is positioned at a radial distance of about 50 mm to a recording area of the optical-information recording medium that is positioned at a radial distance of about 30 mm.
  • the optical-information reproducing system according to the embodiment of the present invention is effective in a case in which the rotational speed of the optical-information recording medium is temporarily not controlled when the optical pickup is moved.
  • the meander period of the groove is set to about 280 kHz as a meander period such that the wobble frequency becomes higher than the 140 kHz that is obtained in the related art.
  • the value of the meander period is not limited thereto.
  • the meander period of the groove can be set using the relationship between the meander period of the groove and the higher-order resonance frequency of the optical pickup.
US12/181,223 2007-07-31 2008-07-28 Optical information reproducing system Abandoned US20090034406A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2007-198892 2007-07-31
JP2007198892A JP4796551B2 (ja) 2007-07-31 2007-07-31 光情報再生システム

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US20090034406A1 true US20090034406A1 (en) 2009-02-05

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US (1) US20090034406A1 (ja)
EP (1) EP2026345B1 (ja)
JP (1) JP4796551B2 (ja)
CN (1) CN101359488B (ja)
AT (1) ATE455349T1 (ja)
DE (1) DE602008000541D1 (ja)
TW (1) TWI385656B (ja)

Citations (4)

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Publication number Priority date Publication date Assignee Title
US7193961B2 (en) * 2002-11-19 2007-03-20 Hitachi Maxell, Ltd. Optical information-recording medium and method for producing the same
US7286461B2 (en) * 2003-08-25 2007-10-23 Sony Corporation Optical disk driving apparatus and method, and recording medium and program used therewith
US20090245053A1 (en) * 2006-08-03 2009-10-01 Senichi Onoda Recording medium, data recording apparatus, data reproducing apparatus and data recording method
US7626907B2 (en) * 2004-05-25 2009-12-01 Ricky Chang Method and apparatus for determining type of digital versatile disc

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JP4114732B2 (ja) * 2001-04-18 2008-07-09 株式会社リコー 対物レンズアクチュエータ
JP2003045053A (ja) 2001-07-30 2003-02-14 Ricoh Co Ltd 対物レンズ駆動装置、光ピックアップ装置及び光ディスク装置
JP2003187459A (ja) * 2001-12-19 2003-07-04 Sony Corp ディスク記録媒体
TWI343051B (en) * 2003-07-29 2011-06-01 Samsung Electronics Co Ltd Method and apparatus for recording and reproducing pointing information, and information storage medium
KR100524999B1 (ko) * 2004-01-13 2005-10-31 삼성전자주식회사 광픽업 액튜에이터
JP2005293650A (ja) * 2004-03-31 2005-10-20 Matsushita Electric Ind Co Ltd 光ディスク装置
RU2376658C2 (ru) * 2004-09-13 2009-12-20 ЭлДжи ЭЛЕКТРОНИКС ИНК. Носитель записи и способ и устройство для записи данных на носитель записи
CN101494071A (zh) * 2006-03-24 2009-07-29 日本先锋公司 信息记录介质、信息记录装置和方法、信息重放装置和方法、以及计算机程序

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7193961B2 (en) * 2002-11-19 2007-03-20 Hitachi Maxell, Ltd. Optical information-recording medium and method for producing the same
US7286461B2 (en) * 2003-08-25 2007-10-23 Sony Corporation Optical disk driving apparatus and method, and recording medium and program used therewith
US7626907B2 (en) * 2004-05-25 2009-12-01 Ricky Chang Method and apparatus for determining type of digital versatile disc
US20090245053A1 (en) * 2006-08-03 2009-10-01 Senichi Onoda Recording medium, data recording apparatus, data reproducing apparatus and data recording method

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Publication number Publication date
TW200923931A (en) 2009-06-01
CN101359488B (zh) 2013-02-27
CN101359488A (zh) 2009-02-04
EP2026345A1 (en) 2009-02-18
JP2009037662A (ja) 2009-02-19
DE602008000541D1 (de) 2010-03-04
EP2026345B1 (en) 2010-01-13
JP4796551B2 (ja) 2011-10-19
ATE455349T1 (de) 2010-01-15
TWI385656B (zh) 2013-02-11

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